Viceroy must be feudal - when is this possible with pagan empire?

So I took a German Catholic king, made him secretly pagan, made him publicly pagan, and then made him an emperor. So he instituted the law of viceroyalty. I summoned some courtiers to his court but he could not make them viceroys because they were not feudal. I looked at the menu for one of his sons and the son could be made a viceroy; apparently his son was feudal even though he had been bred and raised as a pagan.

I tried giving the courtier a county. He became a count, but apparently he did not become feudal.

Is there any way to make a non-feudal character into a feudal character? I would imagine that giving him a landed title should have worked, but it didn't.

Is he Old Germanic or Reformed Germanic? Normally, when playing as a pagan, you can't take the "Adopt Feudalism" decision without reforming your religion. So what I think is going on is that his son had gotten a feudal title while Catholic, become feudal from that, and then converted to Old Germanic. But the father didn't get his feudal title until after he converted to Old Germanic, so he still wasn't eligible to adopt feudalism.

You could reform the religion (if you have the Holy Fury DLC), or you could convert him back to Catholicism just long enough to adopt feudalism, then convert him back to Germanic. Or you could just make his son viceroy instead.

Edit[from Original Questioner]: Thank you! Reforming the religion IS necessary to get a random courtier to become feudal; also, it seems the courtier must be given a county. However, even after the religion is reformed, and even after a guy gets a country and becomes a thane, there must be a duke title available that he is eligible to hold. So I will experiment with the details and post more questions if necessary. Thanks again.